Beam internation devices



Sept. 1, 1959 R. ADLER 2,902,615

BEAM INTERACTION DEVICES Filed April 1, 1954 5 Sheets-Sheet 1 BiosSource Signal Source ROBERT ADLER INVENTOR.

HIS ATTORNEY p 1959 R. ADLER 2,902,615

BEAM INTERACTION DEVICES Filed April 1, 1954 5 sheets-Sheet 5 9 SignalSource FIG.4B

FIG.4C

ROBERT ADLER INVENTOR. I

HIS ATTORNEY.

Sept. 1, 1959 R. ADLER BEAM INTERACTION DEVICES 3 Sheets-Sheet 3 FiledApril 1, 1954 Signal Source FIG. 5

ROBERT ADLE R INVENTOR.

BY flMM HIS ATTORNEY.

United BEAM INTERACTION DEVICES Robert Adler, Northfield, 113., assignorto Zenith Radio Corporation, a corporation of Delaware Application April1, 1954, Serial No. 420,430

17 Claims. (Cl. 313-70) This invention is directed to a new and improvedelectron-discharge device and more particularly to a beaminteractiondevice in which the intensity of one beam of electrons is controlled inaccordance with variations in the intensity of a second electron beam.

The figure of merit of an electron-discharge device employed as anamplifier, modulator, etc., is directly proportional to thetransconductance g and inversely proportional to the grid-cathode andplate-cathode capacities of the device, and its useful frequency rangeis directly related to the figure of merit. Consequently, it may bestated that a tube to be employed as a broadband amplifier should have ahigh transconductance and a minimum of interelectrode capacity. Thelatter requirement is inconsistent with the use of large-area anodesand/or control electrodes, inasmuch as the anode and control electrodecapacities are directly related to the areas of these elements.

One suggested form of electron-discharge device employs two separatebeams projected through an interaction region at right angles withrespect to each other. One of these beams, which carries substantiallyless cur rent than the other of the beams, is intensity-modulated bymeans of a control grid. The changes in intensity of the first beamresult in corresponding variations in space charge density in the commonspace traversed by the two beams so that the second or high-current beamis to a certain extent velocity-modulated in accordance with theintensity-modulation of the low-current beam. Another somewhat similarproposal employs two electron beams projected in opposite directionsalong parallel paths closely adjacent to each other. In this device,deflectionmodulation of one beam produces space charge variations in theregion between the two beams so that the second beam is similarlydeflection-modulated. Each of the described prior-art devices representsan attempt to modulate an electron stream without the use ofconventional deflection plates or a conventional intensit -control grid.However, devices of this type have not been markedly successful and havenot been adopted commercially because the useful gain available frommodulation ofone beam in accordance with variations in a second beam issmall as compared to the amplification which may be achieved by moreconventional tubes.

It is an object of this invention, therefore, to provide a new andimproved electron-discharge device having a relatively high figure ofmerit and suitable for use as a broad-band amplifier.

It is afurther object of the invention to provide a new and improvedbeam-interaction electron-discharge device which provides relativelyhigh amplification.

It is an additional object of the invention to provide a new andimproved electron-discharge device which provides high gain with aminimum of external circuits and connections.

It is another object of the invention to provide a new and improvedbeam-interaction device which is simple 2,902,615 Patented Sept. 1,195,9

and expedient to construct and economical to manufacture.

An electron-discharge device constructed in accordance with one aspectof the invention comprises means includ: ing a first electron gun forprojecting a first sheet-like beam of electrons along a first referencepath and means including a second electron gun for projecting a secondsheet-like beam of electrons along a second reference path, a part ofthe second path being coincident with a part of the first referencepath. The. device further includes an additional electrode system,encompassing at least a part of the coincident parts of the referencepaths; this additional electrode system comprises a retarding electrodewhich is associated with and co-operates with the second electron gun toestablish a virtual cathode region in which the intensity of the secondelectron beam is determined by the intensity of the first electron beamControl means are coupled to at least a portion of the first beam andare responsive to an applied signal to control the intensity of thatportion of the first beam. In addition, the device includes output meanscoupled to at least a portion of one of the electron beams'to derive anoutput signal therefrom.

An electron-discharge device constructed in accordance with anotheraspect of the invention comprises means including a first electron gunfor projecting a first sheetlike beam of electrons along a firstreference path .and means including a second electron gun for projectinga second sheet-like beam of electrons along a second reference path withincrements of each of the two electron beams intercepting more than onesimilar increment of the other beam. Two additional electrode systemsare included in the device; these additional electrode systems areassociated with and co-operate with the electron guns to establish twospaced electron-interaction regions in each of which one of the electronbeams is controlled by the other of the beams. Control means are coupledto at least a portion of the first electron beam and are responsive toan applied signal to modulate that portion of the first beam. Inaddition, the device includes output means coupled to at least a portionof one of the electron beams to derive an output signal therefrom.

The features of the invention which are believed to be novel are setforth with particularity in the appended claims. The organization andmanner of operation of the invention, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals indicate like elements in all figures, andin which:

Figure 1 is a cross-sectional view of an electron-dis charge deviceconstructed in accordance with the lllVfll'l: tion and includes aschematic representation of an amplifier circuit for the device;

Figure 2 is a view of the electrode systems of the tube shown in Figure1, taken along line 2-2 therein;

Figure 3 is a schematic representation of an electrondischarge devicecomprising another embodiment of the invention;

Figures 4A, 4B and 4C are explanatory diagrams illustrating certainelectrical characteristics of the electron tube of Figure 3;

Figure 5 is a schematic representation of another embodiment of theinvention; and

Figure 6 is an explanatory diagram employed to describe the operation ofa portion of the device of Figure 5.

The embodiment of the invention illustrated in Figure 1 comprises anelectron-discharge device 10 including a first electron gun 11 and asecond electron gun 12 both mounted within a single evacuated envelope13. Electron gun 11 comprises a cathode 14, a first focusing electrode15, and an accelerating electrode 16. An additional electrode system 21is associated with gun 11 and comprises a pair of focusing electrodes17, a retarding electrode or grid 18 and an anode 23; the electrodes ofgun 11 and system 21 are disposed in the order named along a referenceplane A. Focusing electrode 15 may comprise a sheet of conductivematerial including an aperture 19 which is symmetrical with respect toreference plane A, and accelerator 16 may be of similar construction andmay include an aperture 20 aligned with reference plane A. Focusingelectrodes 17 may be constructed from conductive rods or similarsuitable elements, and grid 18 may comprise a plurality of conductivewires mounted on a pair of support elements 22 and spaced from eachother in a direction perpendicular to the plane of the drawing. Electrongun 12, which is preferably disposed symmetrically with respect toreference plane A opposite gun 11, includes a cathode 24, a focusingelectrode 25 having an aperture 26 encompassing plane A, and anaccelerating electrode 27 including a slot 28 which is aligned with thereference plane. A second electrode system 36 is associated with gun 12and includes a pair of focusing electrodes 29, a retarding electrode inthe form of a grid 30, and an anode 31 which may be electricallyconnected to or formed integrally with anode 23 of system 21. Anodes 23and 31 include individual apertures 34 and 35 respectively, the twoapertures encompassing reference plane A.

As thus far described, the individual electrodes of guns 11 and 12 andelectrode systems 21 and 36 may be constructed to be essentially similarto each other; in other words, the physical and electricalcharacteristics of cathodes 14 and 24 may be made as nearly identical aspossible, focus electrodes 15 and 25 may have substantially similarconfigurations and may be made from the same conductive material, andthe various other electrodes in each system may similarly be identicalin construction to the corresponding electrodes of the other system.

As indicated in Figure 2, which shows the electrode systems of devicefrom a different aspect, it is preferred that the electrodes of the tubebe substantially greater in height than the width of the aperturesformed in the electrodes. Furthermore, in this embodiment of theinvention, the two electrode systems are displaced with respect to eachother by an acute angle designated 0. This view also shows more clearlythe relative size and position of a control electrode or grid 32included in electrode system 21 and positioned to be substantiallyco-planar with the grid elements of retarding electrode 18. An anode orcollector electrode 33 is positioned intermediate anode 31 and retardingelectrode 30 and extends transversely of reference plane A, as indicatedin Figure l; anode 33 is mounted above apertures 34 and 35 so that itintercepts only the electron stream developed by gun 12 and translatedthrough system 36.

Figure 1 also shows a simplified schematic circuit for tube 10. Cathode14 is connected to focus electrodes and 17 and is also connected to asource of reference potential, here indicated as ground. Similarly,cathode 24 and focus electrodes 25 and 29 are all interconnected and areconnected to ground. Accelerating electrodes 16 and 27 are eachconnected to a source of positive unidirectional operating potential Bwhereas anodes 23 and 31 are conductively coupled to a second source ofpositive operating potential 13 Collector electrode 33 is connectedthrough a load resistor 86 to another source of positive unidirectionalpotential 13 Retarding electrodes 18 and 30 are individually coupled toa variable bias potential source 37, and control electrode 32 is coupledto a single source 38.

The operation of electron-discharge device 10 may perhaps best beunderstood by first considering the somewhat simpler embodiment of theinvention illustrated in Figure 3. In this embodiment, a dischargedevice 39 comprises a first electron gun 40 and a second electron gun41. Electron gun 40 includes a cathode 42, a control electrode 43, afocusing electrode 44, and an accelerating electrode 45. The electrodesof system 40 are arranged symmetrically with respect to a reference pathindicated by short dash line C; electrodes 44 and 45 are provided withsuitable apertures centered about the reference path. Electron gun 41comprises a cathode 46, a focusing electrode 47, and an accelerator 48.An additional electrode system 49 is associated with and cooperates withelectron gun 41; system 49 includes a focusing electrode 50, a retardinggrid 51, and an accelerating electrode 52. The electrodes of gun 41 andsystem 49 may be essentially identical in construction with thecorresponding elements of electron gun 12 and electrode system 36 ofFigure 1; the individual electrodes are preferably symmetricallyarranged about a reference path indicated by dash line E.

As indicated in the drawing, electron guns 40 and 41 are preferablyangularly displaced with respect to each other so that beam referencepaths C and B would normally intersect. However, as will be explainedmore completely hereinafter, the two reference paths do not cross butare made to coincide in part with each other. A solenoid 53 is mountedwithin tube 39 in the general region in which the two reference pathswould normally cross; the axis of the solenoid extends perpendicularlyto the plane of the drawing. Coil 53 is preferably wound from extremelyfine wire so that it intercepts only a very small portion of the twoelectron beams generated by guns 40 and 41; the coil may be mounted on apair of insulating support members 54 formed from ceramic material,mica, or any other suitable insulator. A col' lector electrode 55 isdisposed transversely of reference path E on the side of solenoid 53opposite electrode system 49.

It will be recognized by those skilled in the art that electron gun 41and electrode system 49 together comprise a simplified version of agated-beam tube. In order to understand the operation of tube 39,operation of this section of the tube will first be consideredindependently of the operation of electron gun 40. For this purpose,cathode 46, focusing electrodes 47 and and retarding electrode 51 mayall be connected to a source of reference potential, here taken asground. Accelerating electrodes 48 and 52, on the other hand, areconnected to suitable sources of unidirectional positive operatingpotential generally indicated as B+. Coil 53 is connected throughaccelerator 52 to positive D.C. source B+. The coil is also connected toa source of operating potential shown as a battery 88, a suitablevariable resistor 56 being included in the coil circuit. Collectorelectrode is also connected through a load resistor 87 to positiveoperating potential source B+; it will be understood that the actualoperating potentials applied to anodes 48, 52 and 55 need notnecessarily be the same.

When the apparatus of Figure 3 is placed in operation, a stream ofelectrons emitted from cathode 46 is focused and accelerated as itpasses through the apertures of electrodes 47 and 48 to form asheet-like beam of electrons centered about reference path E. The termsheet-like beam, as used throughout this specification and in theappended claims, refers to any electron stream having one characteristiccross-sectional dimension which is very much smaller than the other.Preferably, the sheet-like beam may be of elongated rectangularconfiguration, in accordance with the indicated configuration ofaccelerator slot 20 (Figure 1).

As the beam emerges from the slot in accelerator 48, it is again focusedas it passes through the aperture in electrode 50. Subsequently, thebeam passes through retarding grid 51 and continues along path E,entering the magnetic field within solenoid 53. The magnetic field ofthe coil deflects the electron beam so that it impinges upon collectoranode 5 5, which may be made relatively large in size to insureinterception of the entire beam over a reasonable range of magneticfield intensities. If"

the beam is sharply focused, a major portion oftheelectrons passesthrough the aperture in anode 52 to impinge ultimately upon anode 55.

The region intermediate accelerator 48 and retarding grid 51 ischaracterized by a high space-charge density, providing the properelectrode spacings and voltagesare maintained, as exemplified bygated-beam tubes such as the commercial type 6BN6. This highspace-charge density region constitutes a virtual cathode, provided theoperating potential on retarding grid 51 is low enough so that a portionof the electron beam is reflected back toward accelerator 48. Foranygiven operating condition, there exists a plane of minimum potentialindicated by dash line 57 within this virtual cathode region. Ifelectrons from an external source areintroduced into the virtual cathoderegion, the plane of minimum potential tends to move toward cathode 46,as indicated by dash line 58, and the number of electrons passingthrough retarding electrode 51 to reach the slot in accelerator 52 maybe sharply reduced.

If electron gun 40 is biased beyond cut off' and a variable voltage isapplied to grid 51, the operating characteristic of the apparatus ofFigure 3 corresponds generally to that shown in Figure 4A, in which irepresents the plate current drawn by anode 55 and is plotted against 2the voltage applied to the retarding grid 51. This operatingcharacteristic is a familiar step-function typicalof devices of thegated-beam type.

In order to determine the operating characteristics of electron gun 40,cathode 42 and focus electrode 44 may be connected to ground potentialand accelerator 45 may be connected to a suitable source of positiveoperating potential B+. At the same time, all of the electrodes of gun41 and-system 49 may be interconnected. to each other and to positiveoperating potential source B+. A variable voltage may then be applied tocontrol electrodev 43, as from a signal source 59. Electron gun 40 thengenerates a stream of electrons which pass through control electrode 43,and are focused and accelerated into a sheet-like beam as they traversethe apertures in electrodes 44' and 45. The electron beam from gun 40follows path C and enters the magnetic field of solenoid 53; themagnetic field deflects the electron beam so that path C extends insubstantial coincidence with path E and passes through the aperture inaccelerator 52 to impinge upon the various electrodes of gun 41 andsystem 49. By varying the potential of control electrode 43, the gridvoltage-plate current characteristic illustrated in Figure 4B is.obtained. In Figure 4B, a symbol 1' refers to the total currentcollected by the electrodes of gun 41 and system 49 and e represents thepotential applied to control electrode 43.

For operation in accordance with the invention, electron gun 41 andelectrode system 49 are reconnected as illustrated and placed inoperation with retarding electrode 51 biased to develop a preselectedplate current I (Figure 4A). In the illustrated embodiment, I is takenas the current intercepted by anode 55 with retarding electrode51grounded. Moreover, the strength of the. magnetic field developed bysolenoid coil 53 is adjusted so that a substantial portion of theelectron stream from gun 40 passes through the aperture in accelerator52 and is projected into the virtual cathode region between electrodes50 and 51; control of the magnetic field strength may be achieved byadjusting variable resistor 56 to vary the current through coil 53.

With both electron guns in operation, and with a substantial portion ofthe beam from gun 40 projected into the virtual cathode regionestablished by electrode system 49, the current drawn-by anode 55 variesin accordance with curve i (Figure 4C) as the voltage e on control grid43 is varied. For convenience, the beam current i of electron gun 40 issimilarly plotted to the same scale in Figure 4C. For any grid'voltageat which the negative slope of curve is is greaterin absolute valuethan: the positive slope-of curve' i the rate of decrease of the currentat plateexceeds-the rate of increase ofthev beam current of gun; 40. Ithas-been found that the interaction factor for the electron beamdeveloped by gun 41 and translated through-system 49, which factor maybegun 40 and the intensity of the electron beam from gun 41 is controlled,in the virtual cathoderegion established by retarding electrode 51'andfocus electrode 50-, in ac? cordance with the intensity of the beamfrom gun '40. Accordingly, the signal applied-to grid 43 appears inamplified inverted form at.collector electrode 55. The two electronbeams are elfectively segregated from each other by the magneticfield ofcoil 53 according to the. direction from which theelectrons enters themagnetic field.

Tube 39 may be constructed to provide a substantial amount-of gain, butmay not achieve as much amplifications as may be realized in a two-stageamplifier constructed with conventional grid-control tubes. In theembodiment of'the invention illustrated in Figures 1 and 2, the gain iseffectively cascaded'to provide even greater amplification so thatseveral tubes may be replaced by a single device without sacrificinggain. When tube 10 is placed in operation, a stream of electrons emittedfrom cathode 14 is focusedand' accelerated as it passes throughapertures 19- and' 20 of electrodes 15 and 16 to form" a sheet-like beamof electrons which enter the interaction regionor virtual cathodeestablished by focusing electrodes 17 and" retarding grid 18;

Similarly, a second stream ofelectrons is developed at cathode 24-' andis-focused and accelerated as it passes through electrodes 25, 27 and29. Each of the electron beams continues through anode slots 34 and 35and extends into the interaction region of the oflher beam, so that achange in intensity of one beam results in an amplified change ofopposite sense in the other beam. Stated differently, an increase in theintensity of electron beam generated by gun 11 and translated throughsystem 21 causes an even greater decrease in the intensity of theelectron beam developed in electron gun 12 and trans lated throughsystem 36, which, in turn, results in an even further and greaterincrease in the intensity of the beam fromgun 11-.

If'the two beams were aligned directly opposite to each' other, thedevice would; be unstable or would tend to produce oscillation,sincejany change in intensity of either beam would continue to build upuntil the two beams reached their respective maximum and minimumintensities. This instability is avoided, in this embodiment, by.angularly displacing the electrodes of the two systems while maintainingtheir substantial symmetry about a common center'plane as illustrated inFigure 2 so that their respective reference paths intersect within planeA at an acute angle 0. Moreover, the means employed for modulating theintensity of one of the beams, control grid 32 is so located that itintercepts only a fractional portion of the beam. Consequently,with'both sections of the tube in operation, a signal to be amplifiedmay be applied fromsource 38 to control grid 32. If theapplied signalinstantaneously increases the potential of electrode 32, the fractionalportion of the first electron beam, developed in system 11, is increasedin intensity so that more electrons pass through the control electrodeand through anode apertures 34 .and 35 and enter the second beaminteraction space. betweenretarding electrode 30 andfocusing electrodes29. This increases the space charge density within a limited. portion60a of interactionspace60, and causesthe point of. minimumpotential';within that space to migrate. toward cathode 24; for example,the plane of minimum potential might move from the location indicated inFigure l by dash line 61 to the location indicated by dash line 62. Asaresult, fewer electrons are able to leave interaction space portion 60aand traverseslots 34 and 35 to reach the first interaction space 63between focusing electrode 17 and retarding electrode 18; in otherwords, the intensity of the second electron beam is reduced. However, asshown in Figure 2, the portion of the second electron beam which hasbeen reduced in intensity does not extend into the portion 63a ofinteraction space 63 from which the electrons controlled in intensity bygrid 32 emerge. Rather, the reduced-intensity portion of the secondelectron beam enters a different portion 63b of interaction space 63.Because fewer electrons from the second beam now enter beam-interactionspace 63b, the potential minimum within that part of the firstbeam-interaction space tends to migrate toward retarding electrode 18and the intensity of that portion of the first beam which passes throughspace 63b is increased. This intensified portion of the electron beamextends into a second portion 60b of interaction space 60 and acts todecrease the intensity of that part of the second electron stream whichextends through interaction region 60b. So long as the product of theinteraction factors of the two interaction regions 60 and 63 is greaterthan unity, the device functions as a cascade amplifier, the signalincreasing inintensity until it finally appears in greatly amplifiedform as collected by anode 33.

It will be recognized that the signal appearing across load resistor 86,which is proportional to the beam current collected by anode 33, is ofopposite polarity with respect to the signal applied to grid 32 fromsource 38. However, signals of the same polarity as the applied signalmay be derived from the device if anode 33 is positioned to interceptthe final portion of the beam generated by system 11 rather than thesecon beam, generated in system 12. To achieve this effect, anode 33 maybe replaced by a similar anode 69 disposed intermediate retardingelectrode 18 and anode 23 at the ends of those electrodes oppositecontrol grid 32. For push-pull operation, a second control grid 68 maybe mounted opposite grid 32 between anode 31 and focus electrodes 29, asindicated in Figure 2, and both anodes 33 and 69 may be provided so thatfractional portions of both beams may be initially modulated and theamplified signal developed by both beams may be collected.

Separate bias source connections for retarding electrodes 18 and 30 areindicated in Figure 1, since minor variations in the potentials of thoseelectrodes may be necessary to achieve optimum performance. Preferably,however, these electrodes should be operated at close to cathodepotential and, for a given tube design, may well be grounded. It will beunderstood that although indi-= rectly heated cathodes have beenillustrated, directly heated emitters may be employed. v

The embodiment of the invention illusrated in Figures 1 and 2 may beconstructed to have a relatively high transconductance. Moreimportantly, the relatively small sizes of the control electrodes andfinal anodes of the device result in substantially reduced grid-cathodeand plate-cathode capacitances as compared to conventional tubes, sothat the figure of merit of tube is very high. Consequently, the tubefunctions efliciently as a broad band amplifier and may replace severalstages of conventional amplifier circuits for a given application. Thefrequency range of the device is limited primarily by the effectivebeam-interaction time, that is to say, the upper frequency limit foreffective operation of the device depends upon the time necessary forchanges in space charge density in the interaction or virtual cathoderegions 60 and 63 to be reflected in changes in beam intensity. Forelectrode dimensions similar to those of the commercially available6BN6, effective operation may be achieved at least as high as theintermediate frequency of 41.25 megacycles normally employed in domestictele- 8. vision receivers. Practical manufacturing considerations arethe principal controlling factors with respect to frequency range;generally speaking, the smaller the electrode slot dimensions and thesmaller the spacing between electrodes, the higher the effectivefrequency range.

The increase in gain achieved in tube 10, as compared to tube 39 ofFigure 3, results from the fact that individual portions or incrementsof each of the electron beams intercept more than one similar incrementof the other beam. Thus, in Figure 2 the vertical increment of the beamfrom gun 11 indicated by dash lines intercepts increments of the beamfrom gun 12 as shown by dash lines 66 and 67. The angular inclination ofthe paths of the two beams within their common center plane A, whichresults from the angular displacement of gun 11 and elect-rode system 21with respect to gun 12 and system 36 by angle 0, comprises one simpleand effective means for cascading the two beams. The same effect may, ofcourse, be obtained by substituting a multiplicity of electron guns andelectrode systems for the illustrated components 11, 12, and 2-1, 36 sothat individual electron beams are substituted for the increments of thetwo beams developed in tube 10. Moreover, it is not essential that thebeams of a device such as tube 10 follow a common center plane, so longas increments of each beam intercept respectively different incrementsof the other beam in the two different interaction regions.

Still another means for achieving cascaded gain is schematicallyillustrated in the embodiment of Figure 5, which is in many respectssimilar to that of Figure 1. The individual elements of electron guns 11and 12 and electrode systems 21 and 36 are included in the electron tubeillustrated in Figure 5; as before, the individual electrodes aresymmetrically arranged about center plane A. For convenience, theadditional control electrode 68 and anode 69 necessary for push-pulloperation have been omitted from Figure 5. Other minor modificationshave been illustrated; for example, the leads for focus electrodes 15,17, 25 and 29 are brought out separately and are connected to potentialsources which are negative with respect to cathode potential. Moreimportantly, and as more clearly indicated in the view of Figure 6, intube 70 the electron guns and associated electrode systems are notangularly displaced with respect to one another. Instead, the offsetrelationship of individual increments of the electron beams necessaryfor effective cascade amplification is achieved by individuallydeflecting the two electron streams.

A first magnetic deflection system, schematically illustrated by a pairof pole pieces 71 and 72, is mounted adjacent electrode system 21. Asimilar magnetic deflection system comprising pole pieces 73 and 74 isassociated with electrode system 36. The two magnetic deflection systemsmay be relatively simple in form and may comprise permanent magnetstructures essentially similar to the ion-trap devices familiar in thecathoderay tube art. The first magnetic deflection system 71, 72develops a first magnetic field, generally indicated by arrow 75, whichtends to deflect the electron beam from gun 11 upwardly as indicated bydash lines 76 in Figure 6. The magnetic field developed by system 73, 74is of opposite sense, as indicated by arrow 77 in Figure 5, so that theindividual increments of the beam from gun 11 are deflected in theopposite direction as they enter the region between anode 3'1 andretarding electrode 30, as indicated by the extensions of dash lines 76in Figure 6.

The effect of the magnetic fields in tube 70 upon the electron beam fromgun 12 is illustrated in Figure 6 by dash-dot lines 78. Because thiselectron stream traverses the magnetic fields in the opposite directionfrom the first beam, it is deflected in the opposite sense by eachmagnetic field. Consequently, as the electron beam from gun 12 entersthe field of magnetic deflection 73, 74 it is deflected upwardly;subsequently, as this beam enters the field of system 71, 72, the senseof the deflection is reversed. Accordingly, it will be seen that themagnetic deflection systems segregate the two beams in accordance withtheir direction of movement so that individual increments of each of theelectron beams developed in tube 70 intercept more than onecorresponding increment of the other of the electron beams so thatcascade action is achieved. In other words, each increment of the electron beam from gun It may be said to coincide with one increment of thebeam from gun 12 in interaction region 63; the same increment of thebeam from gun 11 is coincident with an entirely different increment ofthe beam from gun 12 in interaction region 60.

In all other material respects, the operation of tube 70 may beessentially similar to that of tube 10, so that the functionaldescription of the tube need not be repeated. Tube 70 may be somewhatsimpler to construct, since it is not necessary to angularly displacethe electron guns and their associated electrode systems with respect toeach other. Moreover, if electromagnetic deflection systerns aresubstituted for the permanent magnet stmcture 71-74, the offset of theindividualincrements of the two electron beams with respect to eachother may be adjusted for optimum performance.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from the invention in its broader aspects. The aim ofthe appended claims, therefore, is to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

I claim:

1. An electron-discharge device comprising: means including a firstelectron gun for projecting afirst sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, a part of which is coincident with a part of said firstreference path; means, including an additional electrode systemencompassing coincident parts of said reference paths and comprising aretarding electrode associated with and co-operating with said secondelectron gun, for establishing a virtual cathode region in which theintensity of said second electron beam is determined by the intensity ofsaid first electron beam through direct electron-interaction betweensaid beams; control means coupled to at least a portion of said firstbeam and responsive to an applied signal for controlling the intensityof said portion of said 'first electron beam; and output means coupledto 'at least a portion of one of said beams for deriving an outputsignal therefrom.

2. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, a part of which is coincident with a part of said firstreference path; means including an additional electrode systemencompassing coincident parts of said reference paths and comprising aretarding electrode associated with and cooperating with said secondelectron gun for establishing a-virtual cathode region in which theintensity of said second electron beam is determined by the intensity ofsaid first electron beam through direct:

electron-interaction between said beams; a control electrode disposedtransversely of at least a'portion of said first reference path andresponsive to an applied signal to control the intensity of said portionof said first electron beam; and output means coupledto at least aportion of one of said beams for deriving an output signal therefrom.

3. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirstreference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path,

'10 a part of which is coincident with a part of said firstgreferencepath; means, including an additional electrode system encompassingcoincident parts of said reference paths and comprising a retardingelectrode associated with and co-operating with said second electrongun, for establishing a virtual cathode region in which the intensity ofsaid second electron beam is determined by the intensity of said firstelectron beam through direct electron-interaction between said beams;control means coupled to at least a portion of said first beam andresponsive to an applied signal for controlling the intensity of saidportion of said 'first electron beam; and a collector electrode,disposed transversely of at least a portion of one of said referencepaths, for intercepting at least a portion of one of said beams toderive an output signal therefrom.

4. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, a part of which is coincident with a part of said firstreference path; means, including an additional electrode systemencompassing coincident parts of said reference paths and comprising anaccelerating electrode, focusing means, and a retarding electrodeassociated with and cooperating with said second electron gun, forestablishing a virtual cathode region in which the intensity of saidsecond electron beam is determined by the intensity of said firstelectron beam through direct electron-interaction between said beams;control means coupled to at least a portion of said first beam andresponsive to an applied signal for controlling the intensity of saidportion of said first electron beam; and output means coupled to atleast a portion of one of said beams for deriving an output signaltherefrom.

5. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, a part of which is coincident with a part of said firstreference path; means for segregating said two electron beams; means,including an additional electrode system encompassing coincident partsof said reference paths and comprising a retarding electrode associatedwith and cooperating with said second electron gun, for establishing avirtual cathode region in which the intensity of said second electronbeam is determined by the intensity of said first electron beam throughdirect electron-interaction between said beams; control means coupled toat least a portion of said first beam and responsive to an appliedsignal for controlling the intensity of said portion of said firstelectron beam; and output means coupled to at least a portion of one ofsaid beams for deriving an output signal therefrom.

6. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheet-like beam of electrons alonga. first reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, a part of which is coincident with a part of said firstreference path; means, including a magnetic deflection system, forsegregating the electrons of said two beams in accordance with theirdirection of movement; means, including an additional electrode systemencompassing coincident parts of said reference paths and comprising aretarding electrode associated with and co-opcrating with said secondelectron gun, for establishing a virtual cathode region in which theintensity of said second electron beam is determined by the intensity ofsaid first electron beam through direct electron-interaction betweensaid beams; control means coupled to at least a portion of said firstbeam and responsive to an applied signal for controlling the intensityof said portion of said first electron beam; and output means coupled toat least 11 a portion of one of said beams for deriving an output.signal therefrom.

7. An electron-discharge device comprising; means in-. cluding a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path, angularly displaced with respect to said first path;means, including a magnetic deflection system coupled to said twoelectron beams, for segregating the electrons of said two beams inaccordance with their direction of movement and for deflecting saidfirst beam so that a part of its path of movement coincides with a partof said second reference path; means, including an additional electrodesystem encompassing coincident parts of said reference paths andcomprising a retarding electrode associated with and co-operating withsaid second electron gun, for establishing a virtual cathode region inwhich the intensity of said second electron beam is determined by theintensity of said first electron beam through directelectron-interaction between said beams; control means coupled to atleast a portion of said first beam and responsive to an applied signalfor controlling the intensity of said portion of said first electronbeam; and output means coupled to at least a portion of one of saidbeams for deriving an output signal therefrom.

8. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheet-like beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means, including two additional electrode systems associated with andco-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the other of saidbeams; control means coupled to at least a portion of said first beamand responsive to an applied signal for modulating said portion of saidfirst electron beam; and output means coupled to at least a portion ofone of said beams for deriving an output signal therefrom.

9, An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheet-like beam of electrons along afirst reference path centered about a given reference plane; meansincluding a second electron gun for projecting a second sheet-like beamof electrons in opposition to said first beam along a second referencepath centered about said reference plane with increments of each of saidelectron beams intercepting more than one similar increment of the otherof said beams; means, including two additional electrode systemsassociated with and co-operating with said electron guns forestablishing two spaced electron-interaction regions in each of whichthe electrons in one of said beams are directly controlled by theelectrons in the other of said beams; control means coupled to at leasta portion of said first beam and responsive to an applied signal formodulating said portion of said first electron beam; and output meanscoupled to at least a portion of one of said beams for deriving anoutput signal therefrom.

10. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means including two additional electrode systems associated with andco-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the Other of saidbeams; means, including a control electrode disposed transversely of afractional portion of said reference path and coupled to only afractional portion of said first beam, responsive to an applied signalfor modulating said portion of said first electron beam; and outputmeans coupled to at least a portion of one of said beams for deriving anoutput signal therefrom.

11. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means including two additional electrode systems associated with andco-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the other of saidbeams; control means coupled to at least a portion of said first beamand responsive to an applied signal for modulating said portion of saidfirst electron beam; means including a collector electrode disposedtransversely of a fractional portion of one of said reference paths, forintercepting only a fractional portion of one of said beams to derive anoutput signal therefrom.

12. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means, including two additional electrode systems, each comprising afocusing electrode and a retarding electrode, associated with andco-operating with said electron guns for establishing two spaced virtualcathode regions in each of which the intensity of one of said beams isdetermined by the intensity of the other of said beams through directelectron-interaction between said beams; control means coupled to atleast a portion of said first beam and responsive to an applied signalfor modulating said portion of said first electron beam; and outputmeans coupled to at least a portion of one of said beams for deriving anoutput signal therefrom.

13. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path centered about a given reference plane; meansincluding a second electron gun for projecting a second sheet-like beamof electrons in opposition to said first beam along a second referencepath centered about said reference plane; means for deflecting said twobeams within said plane so that increments of each of said electronbeams intercept more than one similar increment of the other of saidbeams; means, including two additional electrode systems associated withand co-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the other of saidbeams; control means coupled to at least a portion of said first beamand responsive to an applied signal for modulating said portion of saidfirst electron beam; and output means coupled to at least a portion ofone of said beams for deriving an output signal therefrom.

14. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path centered about a given reference plane; meansincluding a second electron gun for projecting a second sheet-like beamof electrons in opposition to said first beam along a second referencepath centered about said reference plane; means, including a magneticdeflection system, for segregating the electrons of said two beams inaccordance with their direction of movement and for deflecting said twobeams so that increments of each of said beams intercept more than onesimilar increment of the other of said beams; means, including twoadditional electrode systems associated with and co-operating with saidelectron guns for establishing two spaced electron-interaction regionsin each of which the electrons in one of said beams are directlycontrolled by the electrons in the other of said beams; control meanscoupled to at least a portion of said first beam and responsive to anapplied signal for modulating said portion of said first electron beam;and output means coupled to at least a portion of one of said beams forderiving an output signal therefrom.

15. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path centered about a given reference plane; meansincluding a second electron gun for projecting a second sheet-like beamof electrons in opposition to said first beam along a second referencepath centered about said reference plane, the electrodes of said secondelectron gun being angularly displaced with respect to the electrodes ofsaid first electrode system so that said second reference pathintersects said first reference path at an acute angle Within said planewith increments of each of said electron beams intercepting more thanone similar increment of the other of said beams; means, including twoadditional electrode systems associated with and co-operating with saidelectron guns for establishing two spaced electroninteraction regions ineach of which the electrons in one of said beams are directly controlledby the electrons in the other of said beams; control means coupled to atleast a portion of said first beam and responsive to an applied signalfor modulating said portion of said first electron beam; and outputmeans coupled to at least a portion of one of said beams for deriving anoutput signal therefrom.

16. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means, including two additional electrode systems associated with andco-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the other of saidbeams; means, including a control grid disposed transversely of afractional portion of said reference path and coupled to only afractional portion of said first beam, responsive to an applied signalfor intensitymodulating said portion of said first electron beams;means, including a second control grid disposed transversely of afractional portion of said second reference path and coupled to only afractional portion of said second beam, responsive to an applied signalfor intensitymodulating said portion of said second electron beam; andoutput means coupled to at least a portion of one of said beams forderiving an output signal therefrom.

17. An electron-discharge device comprising: means including a firstelectron gun for projecting a first sheetlike beam of electrons along afirst reference path; means including a second electron gun forprojecting a second sheet-like beam of electrons along a secondreference path with increments of each of said electron beamsintercepting more than one similar increment of the other of said beams;means, including two additional electrode systems associated with andco-operating with said electron guns, for establishing two spacedelectron-interaction regions in each of which the electrons in one ofsaid beams are directly controlled by the electrons in the other of saidbeams; control means coupled to at least a portion of said first beamand responsive to an applied signal for modulating said portion of saidfirst electron beam; means, including a first collector electrodedisposed transversely of a fractional portion of said first referencepath, for intercepting only a fractional portion of said first beam toderive a first output therefrom; and means, including a second collectorelectrode disposed transversely of a fractional portion of said secondreference path, for intercepting only a fractional portion of saidsecond beam to derive a second output signal therefrom.

References Cited in the file of this patent UNITED STATES PATENTS2,180,957 Hollmann Nov. 21, 1939 2,338,237 Fremlin Jan. 4, 19442,406,370 Hansen et al Aug. 27, 1946 2,457,980 De Forest Jan. 4, 19492,713,648 Gardner July 19, 1955 2,757,337 Gale July 31, 1956

